1. Field of the Invention
The present invention relates to a detection device for detecting an obstacle within a target region by emitting a laser beam to the target region, which is suitable, for example, to be mounted on a moving object such as a vehicle or an airplane.
2. Description of the Related Art
In recent years, in order to improve driving safety, a detection device for detecting an obstacle ahead in a driving direction of a vehicle or the like is mounted, for example, on a family vehicle. The detection device scans a target region with a laser beam to detect the presence or absence of the obstacle within the target region based on the presence or absence of a reflection beam of the laser beam. During normal driving, a scan pattern is set so as to scan with the laser beam the entire target region set ahead in the driving direction of the vehicle. A pulse beam is outputted to a predetermined position on the scan pattern, and the presence or absence of the obstacle at the scan position is detected based on whether or not a reflection beam of the pulse beam is detected by a photo detector. At this time, a distance to the obstacle is measured based on a period between the timing of outputting of the pulse beam and the timing of receiving of the reflection beam thereof.
When the driving direction turns to, for example, the right or the left, it is particularly necessary for the detection device to detect as early as possible an obstacle located in the direction to which the driving direction is turning, in order to achieve adequate control in subsequent driving. During high-speed driving, it is necessary to detect an obstacle located at a distance early enough so that the detection information can be reflected on driving control. When an obstacle is detected ahead in the driving direction of the vehicle, it is particularly necessary to monitor movement of the obstacle and a state thereof in great detail.
JP11-325885A describes a technique for detecting a deviation between a driving direction and a laser beam irradiation direction using an acceleration sensor to align the laser beam irradiation direction with the driving direction.
However, JP 11-325885 A does not describe how to control a laser beam scan state to be adapted to a high-speed driving mode, an obstacle detection mode, and a driving direction changing mode. JP 11-325885 A includes no more description than that the laser beam irradiation direction is merely adjusted so as to suppress the deviation between the laser beam irradiation direction and the driving direction when the driving direction changes.